Vapour cooled discharge tube arrangements



April 29, 1969 p, coLLls ET AL 3,441,081

VAPOUR COOLED DISCHARGE TUBE ARRANGEMENTS Filed Jan. 13, 1967 FIG. 3.

INVENTORS madam/0m MZ m kW/mm Mm Mfu/dz'mgfimw ATTORNEYS United States Patent US. Cl. 165-74 11 Claims ABSTRACT OF THE DISCLOSURE A swirl plate consisting of a ring member with angularly arranged vanes is fitted between-the outlets of the cooling channels of the discharge tube and the vapour exit pipe of the boiler so that a swirling motion is imparted to the water and steam which deflects the water away from the exit pipe.

This invention relates to vapour cooled discharge tube arrangements. By vapour cooled tube is meant a tube in which cooling is effected by utilising heat generated thereby to boil a liquid into a vapour, a major part of the cooling thus occurring due to latent heat. In practice, in the great majority of cases, the liquid is water and the vapour is steam but the invention is not limited to its application to steam cooled tubes since, as will be ap parent, it is applicable to all tubes in which a major part of the cooling is effected by virtue of the latent heat required to boil a liquid into a vapour.

More specifically the invention relates to vapour cooled tube arrangements of the kind in which a tube has a heated structural part thereof provided with cooling channels, for example open ended internal passages or open groove like channels, and said part is in use, immersed for the major portion of its length in liquid (usually water) in a chamber (usually called the boiler) so that liquid in said cooling channels is evaporated to vapour (steam, in the case of water) ejected from said channels, and drawn off from the boiler through an exit pipe for condensation and subsequent return to the boiler. The boiler may be part of the general tube structure, boiler and tube being manufactured to constitute a single unit, or the boiler may be a separate item adapted to receive a tube. The heated structural part provided with open ended internal passages in which liquid is evaporated to vapour is usually an anode and since the anode of a tube is normally operated at a high electrical potential, the pipe from the boiler is usually made of insulation, commonly glass. In most cases the vapour is drawn off through an exit pipe leading from the top of the boiler but in others the vapour flows out into a separate chamber at the side of the boiler and is thence drawn off through an insulating exit pipe leading from said chamber.

In a typical vapour cooled tube arrangement of the kind referred to a tube anode, which is commonly a heavy cylindrical copper structure forming part of the evacuated envelope of the tube, is provided with cooling channels. These may be in the form of grooves though they are preferably constituted by open-ended internal circularly sectioned bores extending parallel to the axis of the tube and arranged in a ring round said axis. The said anode is mounted with the axis of the tube vertical in a surrounding boiler which is filled with liquid up to a level a little below that of the tops of the bores (assuming this type of cooling channel to be employed) and is provided with a liquid inlet near the bottom of the boiler. An exit pipe, usually of glass, for taking off vapour is either fitted to the top of the boiler, or to a separate chamber alongside the boiler and into which vapour from the boiler flows. Vapour generated is drawn off through the exit pipe, cooled and condensed back to liquid, and returned to the boiler inlet pipe, the vapour circulation system being sealed from atmosphere so that the same vapour is used over and over again.

Experience has shown that known vapour cooled tube arrangements of the kind referred to and as exemplified in the immediately preceding paragraph are not as satisfactory for cooling as is desirable and that, when the power of a given tube in a given boiler is increased beyond a certain point, there occurs a pronounced and more or less sudden drop in the effectiveness of cooling and, if the tube is not switched off or the power not considerably reduced, a rapid rise in tube temperature may occur. This is a serious defect. While the utility of the present invention is not dependent upon the correctness and sufiiciency or othewise of the theory now to be advanced, it is believed that the cause of the foregoing defect lies partly in the effectiveness of the boiler exit pipe to draw off vapour becoming reduced when a certain tube power is exceeded. When the liquid is boiled in the cooling channels of the heated structural part of the tube provided therewith, considerable quantities of vapour and suspended liquid are ejected from said passages and when the rate of ejection is high enough a mass of liquid, of more or less ball form, is suspended in the mouth and near the interior of the exit pipe. Also a layer of liquid is formed over the interior I surface of the exit pipe near the boiler. As a result the exit pipe is partially blocked so that there is a great reduction in its effectiveness to draw off vapour and there also oc curs a rise of pressure in the boiler with consequent depression of the level therein to an extent sufficient to prevent proper cooling. The presence of such liquid in the exit pipe of course greatly reduces its effectiveness as an insulator and greatly increases the liability to electrical breakdown.

According to this invention a vapour cooled tube arrangement of the kind referred to is provided in the paths of vapour and liquid ejected from the cooling channels of the heated structural part of the tube to the vapour exit pipe, with means for imparting a rotary or swirling motion to the liquid carried with said vapour whereby at least a substantial portion of the liquid is deflected outwards away from the mouth of said exit pipe. It will be seen that, because a rotary or swirling motion is imparted to the ejected material a substantial measure of centrifugal separation of liquid and vapour occurs, the liquid being flung out towards the internal boiler wall and thus deflected away from the mouth of the exit pipe. Blocking of the exit pipe by liquid is thus eliminated or at least greatly reduced.

Preferably the cooling channels are constituted by internal open-ended passages in the heated structural part of the tube and the means for imparting swirling or rotary motion are situated between the liquid and vapour ejection ends of said passages and the exit pipe. Preferably also the exit pipe leads from the top of the boiler.

The invention is simple and cheap to put into practice. In a preferred embodiment of the invention the means for imparting rotary or swirling motion comprise a ring member which is mounted in the paths of ejected liquid and vapour from the heated structural part towards the exit pipe and is provided with angularly arranged deflector teeth or vanes against which ejected material impinges to change its direction in the required manner. The said teeth or vanes may conveniently be triangular in shape and lie in planes at suitable anglesabout 45 say--to the direct lines of trajectory of the liquid and vapour. Preferably the ring member is attached to and encircles the 3 upper end of the heated part of the tube structure, though it may be mounted in other ways or in other positions.

Preferably a gutter is provided round the mouth of the exit pipe to collect liquid from the interior wall of the exit pipe, said gutter having a return pipe leading back to near, and preferably below, the normal liquid level in the boiler.

An additional liquid separator consisting of a perforated cylinder may be fitted in the mouth of the exit pipe.

If desired a number of additional vanes, which may be curved, may be arranged in a ring round the axis of and near the entrance to the exit pipe said vanes being inclined with respect to radial directions so as to impart added swirling or rotary motion to liquid and vapour on its way to the exit pipe.

Again if desired an open-ended perforated baffle cylinder, of diameter somewhat less than the internal diameter of the boiler, may be provided to extend over the upper part of the boiler from near the liquid level thereof in order to trap liquid flung outwards through the perforations into the space between said cylinder and the boiler wall and return said liquid to the main body of liquid in the boiler.

The invention is illustrated in the accompanying drawings in which FIGURE 1 is a simplified broken away view, partly in section, of a steam cooled tetrode tube arrangement in which the boiler is formed as a structural part of the tube, the tube anode being shown in section; FIGURE 2 is a perspective view to a larger scale showing the swirl ring 10 of FIGURE 1; and FIGURE 3 is a broken away view looking up into the top of the boiler, showing the additional swirl vanes 16 of FIGURE 1.

Referring to the drawing 1 is the anode structure of a known steam cooled tube--e.g. a tetrode. The internal construction and electrodes other than the anode of the tube forrn no part of this invention and, being of any well known design, are not shown. The anode 1 has cylindrical open ended bores 2 arranged in a ring round the tube axis. The upper end of the anode is closed over, vacuum tight, in the usual way, 3 being the sealed off exhaust tail under the protecting cover 4. The anode forms part of the evacuated envelope of the tube as does the ceramic cylindrical part 5 (shown broken away), and part of a flange member 6. Fitted water and steam tight on the outer part of the flange member 6 is a boiler shell 7 which enclosed the anode. The shell has a water inlet pipe 8 in its lower part and, centrally at the top, is fitted a glass exit pipe 9 for steam, The boiler is partly filled with water, the normal Water level, when the tube is in operation, being indicated by the line W. The lower ends of the bores 2 are near the bottom of the boiler in a position to admit free entry of water and the upper ends of said bores are a little above the normal water level W. In operation water is boiled in the bores 2, steam and water are ejected from their upper ends, and steam passes out through the exit pipe to be condensed by a condenser (not shown) and returned to the inlet pipe 8.

As so far described the apparatus is in accordance with well known practice. At high tube powers, however, when large quantities of water and steam are ejected from the upper ends of the bores 2, water construction is liable to be set up in and near the mouth of the exit pipe 9 with the disadvantages hereinbefore mentioned. In order to avoid this defect a swirl ring 10 is fitted to encircle the upper part of the anode above the upper or ejection ends of the bores 2. This ring has teeth or vanes 11 suitably inclined to the direct lines of trajectory from the ejection ends of the bores 2 so that ejected water and steam strike these teeth or vanes which impart thereto a strong swirling or rotary component of motion round the boiler. A suitable construction for the swirling ring 10 is best shown in the perspective view of FIGURE 2 which is to a larger scale than FIGURE 1. It is believed that centrifugal separation between water and steam occurs due to the action of the swirl ring 10. Whether this be the correct theory of operation or not, experiment shows that a large proportion of the water which would otherwise pass more or less directly into the mouth of the exit pipe is deflected outwards towards the boiler wall. In practical experiment with a particular apparatus as so far described it was found that the tube power which could be sustained before serious obstruction occurred in the exit pipe and serious depression of the water level occurred was approximately doubled by fitting the swirl ring 10,

The swirl ring need not be in the position shown nor need it be carried by the anode. It could be carried by the boiler shell.

The drawings show a number of minor improvements any or all of which can be provided if required. One consists of a separator in the form of an open-ended perforated cylinder 12 of smaller diameter than the exit pipe and fitted in the mouth thereof to leave a space 13 between itself and the exit pipe. Steam entering the exit pipe will be swirling and accordingly any water carried by it will be thrown out by centrifugal force. Such water thrown through the perforations of the separator 12 into the space 13 will be shielded from the steam and can run back via a gutter 14 which constitutes another improvement. This gutter 14 is fitted under the top of the boiler shell round the exit pipe to collect water running down from the inside wall of the exit pipe. This water is returned to the main water reservoir of the boiler by a dependent pipe 15 terminating a little below the water level W. A third improvement consists of a number of swirl vanes 16 fitted under the top of the boiler-as shown to the underside of the gutter 14. These are shaped and positioned to provide additional swirling or rotary motion to water and steam which has passed the swirl ring 10. The vanes are angularly disposed to the radii and may be curved, rather like turbine blades, as shown in FIGURE 3. The last minor improvement consists of a perforated open ended axially positioned cylinder 17 spaced from the inner wall of the boiler and extending over the upper part thereof. The purpose of this cylinder is to trap waterwhich has been thrown through its perforations and return it down the cylinder-boiler space to the main water reservoir.

By far the greatest improvement is effected by the swirl plate 10. The other improvements above described are, as stated, relatively minor.

The invention is, of course, not limited to its application to vapour cooled tetrodes but is applicable to vapour cooled discharge tubes generally.

We claim:

1. In a vapour cooled tube arrangement of the type including a boiler for containing liquid coolant therein and having an exit pipe connected to the boiler, and a structural tube part within the boiler for immersion of a major portion of the length of said part in the liquid coolant; said structural part defining discrete cooling channels along a portion of the length of the part, said channels defining first opening means at one end thereof for admitting coolant liquid and second opening means at the further end thereof for emitting vapour in jets therefrom and means aligned with the path of vapour emitted from said channels for imparting a rotary or swirling motion to the liquid carried with the emitted vapour, said means for imparting rotary or swirling motion including a number of deflector teeth lying in the path of the emitted vapour and inclined relative to the path of emitted vapour from said channels for deflecting the liquid carried with emitted vapour outwardly away from the mouth of said exit pipe.

' 2. An arrangement as claimed in claim 1 wherein the cooling channels are constituted by internal open-ended passages in the heated structural part of the tube and the means for imparting swirling or rotary motions are situated between the liquid and vapour ejection ends of said passages and the exit pipe.

3. An arrangement as claimed in claim 1 wherein the exit pipe leads from the top of the boiler.

4. An arrangement as claimed in claim 1 wherein the means for imparting rotary or swirling motion comprise a ring member which is mounted in the paths of ejected liquid and vapour from the heated structural part towards the exit pipe, said ring member being provided with said deflector teeth against which ejected material irn; pinges to change its direction.

5. An arrangement as claimed in claim 4 wherein said inclined teeth are triangular in shape.

6. An arrangement as claimed in claim 4 wherein the ring member is attached to and encircles the upper end of said structural tube part.

7. An arrangement as claimed in claim 1 wherein a gutter is provided round the mouth of the exit pipe to collect liquid from the interior wall of the exit pipe, said gutter having a return pipe leading back to near the normal liquid level in the boiler.

8. An arrangement as claimed in claim 1 wherein an additional liquid separator consisting of a perforated cylinder is fitted in the mouth of the exit pipe.

9. An arrangement as claimed in claim 1 wherein additional vanes are arranged in a ring round the axis of and near the entrance to the exit pipe said vanes being 6 inclined with respect to radial directions so as to impart added swirling or rotary motion to liquid and vapour on its way to the exit pipe.

10. An arrangement as claimed in claim 1 wherein an open-ended perforated baffie cylinder, of diameter somewhat less than the internal diameter of the boiler is provided to extend over the upper part of the boiler from near the liquid level thereof in order to trap liquid flung outwards through the perforations into the space between said cylinder and the boiler wall and return said liquid to the main body of liquid in the boiler.

11. An arrangement as claimed in claim 1 wherein the liquid is water and the vapour is steam.

References Cited UNITED STATES PATENTS 2,160,6l9 5/ 1939 Larrecq 122-488 2,969,957 1/1961 Beurtheret 165-74 X 3,289,022 11/1966 Oberlander 313 CHARLES J. MYHRE, Primary Examiner.

US. Cl. X.R. 105 

